Variable capacity vane compressor with axial pressure device

Abstract: A variable capacity vane compressor has an axial pressure device for applying variable axial pressure to a rotary valve. The rotary valve plate locates in a rotary valve housing and changes the capacity of the compressor due to its rotary position. An actuator member rotates the rotary valve plate in response to varying pressure in the discharge and intake chambers. A control valve supplies a variable control pressure to the actuating member for moving the actuating member to rotate the rotary valve plate. An annular axial pressure chamber is located between the rotary valve housing and the rotary valve plate. A control pressure port leads from the control valve to the axial pressure chamber. A seal member within the axial pressure chamber applies an axial force on a bearing located on the rotary valve plate. The control valve which supplies variable pressure used to vary the actuator member position also supplies the control pressure to the axial pressure chamber.

Description: BACKGROUND OF THE INVENTION 1. Field of the invention: This invention relates in general to variable capacity vane compressors for air conditioning systems, particularly for vehicles, and in particular to an axial pressure device that enhances sealing between a rotary valve plate and a compression housing shoulder. 2. Description of the Prior Art: One type of automotive air conditioning compressor in use is a variable capacity vane compressor. In this type of compressor, a compression housing has a chamber that is oval in shape. A cylindrical rotor extends through the chamber. The rotor has radial vanes mounted to it which slide radially in slots formed in the rotor. Refrigerant at suction pressure enters the compression chamber, with the vanes compressing the refrigerant, which passes outward through a valve. The compressor demand varies according to speed and atmosphere conditions. At highway speed, the demand is usually lower than while idling on a hot day. To vary the capacity, a rotary valve disk or plate mounts in front of the compression housing and in engagement with a shoulder on the compression housing. The valve plate has a slotted perimeter which will change the position of the opening from the intake chamber into the compression chamber depending upon the rotational position of the valve plate. The valve plate is rotatably carried in a rotary valve housing, also known as a rear side block. The particular rotational position of the valve plate will change the quantity of refrigerant introduced between the vanes for compression by changing the timing of the compression cycle. An actuator will rotate the valve plate to selected positions depending upon the changes in the discharge pressure and the intake or suction pressure. In one type, such as shown in U.S. Patent 5,145,327, the actuator member comprises radial projections mounted to the rear side of the rotary valve plate and located within chambers. Each projection serves as a piston. Variable fluid pressure is applied to both sides of each piston. Also, a spring will urge the plate to a minimum delivery position. A control valve supplies a control pressure to one side of each piston, the other side of each piston being at intake pressure. The control valve includes a bellows which has a stem that engages a ball valve. The bellows is located in a portion of the suction chamber. A plunger or bias pin on the opposite side of the ball has one end exposed to discharge pressure. The plunger and the stem of the bellows cooperate depending upon the discharge and intake pressure to selectively apply a control pressure to one side of the pistons for moving the rotary valve plate. In another type of actuator, the rotary valve plate is rotated by a spool piston, such as shown in U.S. Patent 4,838,740. The spool piston moves linearly transverse to the axis of the rotor. The spool piston has a pivot pin that engages the plate to cause it to rotate as the spool piston moves. Patents exist which disclose a variety of control valves for applying pressure to the spool piston to cause it to move in response to intake and discharge pressure. Whether the actuator is a linear piston or a radial projection, the rotary valve plate slidingly engages a shoulder facing rearward on the compression housing. The shoulder surrounds the compression chamber. The valve plate slidingly engages this shoulder as the valve plate rotates. Because the valve plate forms one end of the compression chamber, it is important to have as good a sealing as possible between the rotary valve plate and the compression shoulder. In the type of rotary valve plate wherein the actuating pistons are radially oriented projections mounted to the rear side and radially oriented, variable axial pressure is applied to the rotary valve plate because the rear side of the rotary valve plate is exposed to the chambers containing control pressure for rotating the valve plate. These chambers cause a forward acting axial force to assist in sealing between the face of the valve plate and the compression shoulder. On the other hand, in the type utilizing a linearly movable spool piston, there is no axial pressure applied to the rear side of the rotary valve plate. Consequently, there would be a tendency for leakage to occur between the rotary valve plate and the compression shoulder. If installed very tightly, leakage could be minimized, however friction might make it difficult to rotate the rotary valve plate. SUMMARY OF THE INVENTION The invention provides a compressor of the type defined in the pre-characterising portion of claim 1, having the additional features of the characterising portion of claim 1. In this invention, the actuator is a spool piston type. It is located transverse to the axis of the rotor. A control valve supplies a control pressure to the actuator to cause it to move to rotate the valve plate. The rotary valve plate is located in a rotary valve housing, which also contains the chambers for the spool type actuator piston. An annular axial pressure chamber is located between the rotary valve housing and the rotary valve plate. A control pressure port leads from the control valve to the axial pressure chamber to supply pressurized fluid to the axial pressure chamber. This pressurized fluid varies depending upon the demand on the compressor, and therefore provides a variable axial force on the rotary valve plate. This enhances sealing between the rotary valve face and the compression housing shoulder. In the preferred embodiment, the axial pressure chamber is located in the rotary valve housing. An annular elastomeric seal locates in the axial pressure chamber. An annular bearing locates on the rotary valve plate in engagement with the seal. Control pressure supplied to the seal will cause the seal to exert an axial force on the bearing, which transmits to the rotary valve plate. The bearing allows rotation of the rotary valve plate while the seal remains stationary. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be further described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a partial sectional view illustrating a compressor constructed in accordance with this invention; Figure 2 is another sectional view of the compressor of Figure 1, taken along a section line that is perpendicular to the section shown in Figure 1; Figure 3 is a partial sectional view of the compressor of Figure 1, taken along another section line; Figure 4 is a sectional view of the compressor of Figure 1, taken along the line V-V of Figure 1; Figure 5 is a rear elevational view of the rotary valve plate used with the compressor of Figure 1; and Figure 6 is a sectional view similar to Figure 1, but showing the discharge chamber. DETAILED DESCRIPTION OF THE INVENTION Referring to Figure 1, compressor 11 is shown partly in a sectional view. Compressor 11 is a variable capacity vane type compressor. It includes a compressor housing 13 which has compression chamber 15. As shown in Figure 4, compression chamber 15 is generally oval in configuration. A plurality of vanes 17 mounted in slots on a rotor 19 rotate inside compression chamber 15. Rotor 19 rotates on an axis 21 that is concentric with compression chamber 15. Valves 23 (only one shown) provide for the discharge of refrigerant gas from the compression chamber 15. The refrigerant gas passes to a discharge chamber 16, which is the type as shown in U.S. Patent 5,145,327, Nakajima, et al, September 8, 1992, all of which material is hereby incorporated by reference. Referring again to Figure 1, a rotary valve plate 25 mounts rotationally to the intake side of compressor chamber 15. Rotary valve plate 25 is a disk-shaped member, having an irregular perimeter 27 as shown in Figure 5, which defines slots. As shown in Figure 4, the particular rotational position of rotary valve plate 25 will change the position of the intake opening into the compression chamber 15 and thus the volume of refrigerant introduced between the vanes 17 as rotor 19 rotates. In this manner, the capacity of compressor 11 can be varied. Referring again to Figure 1, rotary valve plate 25 has a face 29 on the forward side that slidingly engages a compression housing shoulder 31. The compression housing shoulder 31 surrounds compression chamber 15. The contact is metal-to-metal between rotary valve face 29 and compression housing shoulder 31. Rotary valve plate 25 will rotate approximately 70 degrees from a fully closed position to a fully open position. Rotary valve plate 25 is carried in a rotary valve housing 33, also called a rear side block. Rotary valve housing 33 mounts stationarily to compression housing 13 and has a central portion 33a. A rear head 35 mounts to the rear of rotary valve housing 33 by bolts. An intake chamber 37 is defined within rear head 35 and surrounds the central portion 33a of rotary valve housing 33. Intake chamber 37 will be at the suction or intake pressure of the refrigerant after it has passed through the evaporator (not shown). An actuator member or piston 39 will rotate rotary valve housing 33 between the minimum and maximum positions. Actuator piston 39 is a spool-type piston, located transverse to the axis 21 of rotor 19. As shown in Figure 2, actuator piston 39 is located in a piston chamber 41 which extends transversely through rotary valve housing 33. The central portion of piston chamber 41 is intersected by a portion of intake chamber 37, thus resulting in two separate sections. Actuator piston 39 has a seal 42 which defines in chamber 41 a suction side 41a, which is on the right side (as drawn) of seal 42, and a control pressure side 41b, which is on the left side (as drawn) of seal 42. Control pressure side 41b is supplied with a control pressure for moving actuator piston 39 to the right in response to change in demand on compressor 11. A coil spring 43 urges actuator piston 39 to the left, which positions rotary valve plate 25 in the minimum capacity position. End caps 45, 47 seal the opposite ends of piston chamber 41. A suction passage (not shown) extends from the intake chamber 37 to the suction side 41a to assure that suction pressure is communicated to the suction side 41a of piston chamber 41. Referring to Figures 1 and 2, the linkage means between actuator piston 39 and rotary valve plate 25 includes in the preferred embodiment a roller 51, which is a small, slidable member locating within an undercut 52 in actuator piston 39. Roller 51 is rotatably supported on a pin boss 53, which is rigidly mounted to rotary valve plate 25. Linear movement of actuator piston 39 causes rotational movement of rotary valve plate 25 through roller 51 and pin boss 53. Referring again to Figure 1, axial piston means exist for applying a variable axial force on rotary valve plate 25 to enhance sealing between rotary valve face 29 and compression housing shoulder 31. The axial piston means includes an annular axial pressure chamber 55 that is located in central portion 33a of rotary valve housing 33. Axial pressure chamber 55 is a groove concentric to rotor axis 21. Axial pressure chamber 55 is rectangular in transverse cross section. Control pressure will be supplied to axial pressure chamber 55, as will be explained subsequently. The axial piston means also includes a seal member or seal ring 57, which is sealingly located in axial pressure chamber 55. Seal ring 57 is a conventional O-ring, circular in transverse cross section. Seal ring 57 will have its rearward side exposed to control pressure in axial pressure chamber 55. An annular bearing 59 is located on a shoulder 61 on rotary valve plate 25. Bearing 59 is a conventional thrust bearing which has one side engaged by seal ring 57 and the other side in contact with shoulder 61. In the preferred embodiment, bearing 59 is a needle-type thrust bearing, with needles located between forward and rearward plates. The forward plate, which is in contact with shoulder 61, will rotate with rotary valve plate 25, while the rearward plate of bearing 59 will remain in stationary engagement with seal ring 57. Seal ring 57 can move axially within axial pressure chamber 55 to exert a variable axial force on bearing 59 to increase and decrease the force of rotary valve face 29 on compression housing shoulder 31. A control valve 62 for supplying control pressure to actuator piston 39 and to axial pressure chamber 55 is shown in Figure 3. Control valve 62 does not appear in Figure 1 because of the different sectional view shown in Figure 1. Control valve 62 includes a bellows 93 which is initially evacuated and mounts within a cavity 63 in the rear head 35. Cavity 63 is in communication with intake chamber 37, thus the exterior of bellows 93 is in communication with intake chamber 37. Bellows 93 has a stem 97 that extends parallel to the rotor axis 21 (Fig. 1) . Stem 97 will move forward and rearward due to expansion and contraction of bellows 93. Stem 97 engages a ball 101 which is located in a ball seat member 103 and urged by a spring 105 to a closed position. Ball seat member 103 is located in rotary valve housing 33. Lateral holes 113 (only one of which is visible in Figure 3) extend outward from ball seat member 103 to allow the discharge of fluid into control pressure chamber 63b in rotary valve housing 33. A bias pin or plunger 109 slidably moves within a plunger passage 111. Bias pin 109 is coaxial with stem 97 and engages the opposite side of ball 101. If bellows 93 expands, stem 97 pushes ball 101 downwards (as drawn) off the seat of seat member 103, and pushing bias pin 109 downwards. Ball 101 then is in an open position to allow flow of fluid from control chamber 63b, through lateral holes 113, and into the suction chamber 37. Conversely, if bellows 93 contracts, spring 105 pushes ball 101 back into the seat of seat member 103, blocking communication between suction chamber 37 and control chamber 63b. As shown in Figure 3, discharge pressure from the discharge chamber 16 of compressor 11, is applied through a passage 65 to the base of plunger passage 111. The pressure thus acts on the bottom end (as drawn) of bias pin 109, urging bias pin 109 toward ball 101. A metered orifice 115 extends from passage 65 to control chamber 63b. Metered orifice 115 is a small diameter drilled hole to allow a continuous selected flow rate of discharge pressure refrigerant to pass into control chamber 63b. A control pressure passage leads to control pressure side 41b of piston chamber 41. A control pressure port leads from control pressure chamber 63b to the axial pressure chamber 55. The control pressure port provides a supply of refrigerant at the control pressure in control chamber 63b to the seal ring 57. The control pressure port thus serves as part of a passage means for supplying a variable control pressure to seal ring 57. At startup, the actuator piston 39 will be located in the position shown in Figure 2. Rotary valve plate 25 will be in the minimum delivery position. Referring to Figure 3, initially the bellows 93 will be contracted and the force of discharge pressure on the end of bias pin 109 plus the force of spring 105 on ball 101 will keep ball 101 closed. Discharge pressure from passage 65 is applied to bias pin 109 and also flows through metered orifice 115 into control chamber 63b, and through the control pressure passage to the control pressure side 41b of actuator piston chamber 41. This causes piston 41 to move to the right (as drawn) from the position shown in Figure 2, rotating rotary valve plate 25. This increases the capacity of compressor 11 by changing the timing of the compression cycle and increasing the volume of refrigerant being compressed. At the same time, discharge pressure is applied through the control pressure port to seal ring 57, which applies an axial force to rotary valve plate 25. This causes rotary valve plate 25 to more tightly bear against compression housing shoulder 31. Consequently, at high pressures within compression chamber 15, a high axial force proportional to the discharge pressure is applied against the rotary valve plate 25 to enhance sealing with compression housing shoulder 31. At highway speeds and at cooler conditions, the demand will decrease on compressor 11. The discharge pressure and the suction pressure in suction chamber 37 will decrease. The lower suction pressure causes bellows 93 to expand. When the force due to the expansion of bellows 93 exceeds the force due to spring 105 plus the force due to discharge pressure acting on bias pin 109, stem 97 will push ball 101 off of its seat. This exposes control chamber 63b to pressure in suction chamber 37. Some of the pressure can then bleed through passage (Fig. 3), control chamber 63b, lateral holes 113 into the suction chamber 37. This decreases the force on actuator piston 39, causing it to move to the left (as drawn) to rotate valve plate 25, reducing the capacity of compressor 11. At the same time, the lower pressure in control chamber 63b is applied through the control pressure port to the axial pressure chamber 55. The reduced pressure on seal ring 57 reduces the axial force on rotary valve plate 25. This allows rotary valve plate 25 to more freely rotate back to a lesser capacity position. Consequently, the axial force in rotary valve plate 25 varies in proportion to the control pressure applied to actuator piston 39. This invention has significant advantages. Applying an axial force to the rotary valve plate enhances sealing between the rotary valve face and the compression housing shoulder. Varying the force in response to demand of the compressor avoids applying too much force when the valve needs to rotate to a new position.

Claims: A compressor (11) having a compression housing (13) defining a compression chamber (15) with an axis (21), a rotatably driven rotor (19) having a plurality of radial vanes (17) and extending axially through the compression chamber (15), an intake chamber (37) on one end of the compression chamber (15) and a discharge chamber (16) on the other end of the compression chamber (15), the compression housing (13) having a compression housing shoulder (31) that is substantially perpendicular to the axis and facing the intake chamber (37), a rotary valve housing (33) mounted to the compression housing (13) in the intake chamber (37), a rotary valve plate (25) rotatably carried in the valve housing (33) and having a rotary valve face (29) in sliding contact with the compression housing shoulder (31) and configured to vary the position of an opening from the intake chamber (37) to the compression chamber (15), a linearly movable actuator member (39) engaging the rotary valve plate (25) by a pivot pin (53) for rotating the rotary valve plate (25), and a control valve (62) for supplying a variable control pressure to the actuator member (39) for moving the actuator member and rotary valve plate (25) in response to varying pressures in the intake chamber (37) and discharge chamber (16) and an annular axial pressure chamber (55) located between the rotary valve housing (33) and the rotary valve plate (25), characterized by: a control pressure port leading from the control valve (62) to the axial pressure chamber (55) to supply pressurized fluid to the axial pressure chamber (55) to provide a variable axial force on the rotary valve plate (25) to enhance sealing between the rotary valve face (29) and the compression housing shoulder (31). The compressor according to claim 1 wherein at least a portion of the axial pressure chamber (55) is located within the rotary valve housing (33). The compressor according to claim 1, wherein the axial pressure chamber (55) is located within the rotary valve housing (33), and wherein the compressor further comprises: an annular seal member (57) sealingly located within the axial pressure chamber (55), the seal member applying an axial force to the rotary valve plate (25) in response to the pressurized fluid from the control pressure port. The compressor according to claim 3, wherein the compressor further comprises: an annular bearing (59) on the rotary valve plate (25), the seal member engaging the bearing (59) and in response to the pressurized fluid from the control pressure port, applying an axial force to the bearing on the rotary valve plate. The compressor according to claim 3 or claim 4, wherein the annular seal member (57) is elastomeric, the seal member moving axially in response to the pressurized fluid from the control pressure port. The compressor according to any one of claims 3 to 5, wherein the seal member (57) is circular in transverse cross-section. The compressor according to any preceding claim, wherein the pressurized fluid supplied through the control pressure port is substantially the same as the control pressure supplied to the actuating member (39).

Inventors: BEARINT DAVID E, BEARINT, DAVID E.
Applicants: ZEXEL USA CORP, ZEXEL USA CORPORATION
Application year: 1994
Main classification: F04C29
IPC codes: F04C28, F04B1, F04C18, F04C27